The unit of local government imposing an impact fee may amend the comprehensive road improvement plan no more than once per year, provided the cumulative amendments do not exceed 10% of the total plan in terms of estimated project costs. If a proposed plan amendment will result in the cumulative amendments to the plan exceeding 10% of the total plan, then the unit of local government shall follow the procedures set forth in Section 5-905 of this Division. Regardless of whether the Comprehensive Road Improvement Plan has been amended, the unit of local government imposing an impact fee shall update the comprehensive road improvement plan at least once every 5 years. The 5 year period shall commence from the date of the original adoption of the comprehensive road improvement plan. The updating of the comprehensive road improvement plan shall be made in accordance with the procedures set forth in Section 5-905 of this Division.